University of Worcester Worcester Research and Publications

Ultrastructure and Physical Properties of an Adhesive Surface, the Toe Pad Epithelium of the Tree Frog, Litoria caerulea.

Scholz, I., Barnes, W.J.P., Smith, Joanna and Baumgartner, W. (2009) Ultrastructure and Physical Properties of an Adhesive Surface, the Toe Pad Epithelium of the Tree Frog, Litoria caerulea. Journal of Experimental Biology, 212 (2). pp. 155-162. ISSN 0022-0949


Download (1MB) | Preview


Knowledge of both surface structure and physical properties such as stiffness and elasticity are essential to understanding any adhesive system. In this study of an adhesion surface in the tree frog, Litoria caerulea White, a variety of techniques including atomic force microscopy were used to investigate the microstructure and properties of an epithelium that adheres through wet adhesion. Litoria toe pads consist of a hexagonal array of flat-topped epithelial cells, separated by mucus-filled channels. Under an atomic force microscope, this `flat' surface is highly structured at the nanoscale, consisting of a tightly packed array of columnar nanopillars (described as hemidesmosomes by previous authors), 326±84 nm in diameter, each of which possesses a central dimple 8±4 nm in depth. In fixed tissue (transmission electron microscopy), the nanopillars are approximately as tall as they are broad. At the gross anatomical level, larger toe pads may be subdivided into medial and lateral parts by two large grooves. Although the whole toe pad is soft and easily deformable, the epithelium itself has an effective elastic modulus equivalent to silicon rubber (mean Eeff=14.4±20.9 MPa; median Eeff=5.7 MPa), as measured by the atomic force microscope in nanoindentation mode. The functions of these structures are discussed in terms of maximising adhesive and frictional forces by conforming closely to surface irregularities at different length scales and maintaining an extremely thin fluid layer between pad and substrate. The biomimetic implications of these findings are reviewed.

Item Type: Article
Additional Information:

Staff and students at the University of Worcester can access the full-text via Library Search. External users should check availability with their local library or Interlibrary Requests Service.

Uncontrolled Discrete Keywords: tree frog, adhesion, electron microscopy, effective elastic modules, tribiology
Subjects: Q Science > Q Science (General)
Q Science > QL Zoology
Q Science > QH Natural history > QH301 Biology
Divisions: College of Health, Life and Environmental Sciences > School of Science and the Environment
Related URLs:
Depositing User: Joanna Smith
Date Deposited: 25 Oct 2012 10:15
Last Modified: 08 Jun 2021 09:23

Actions (login required)

View Item View Item
Worcester Research and Publications is powered by EPrints 3 which is developed by the School of Electronics and Computer Science at the University of Southampton. More information and software credits.